Clinical Investigation
Carotid Arterial Evaluation
What Do Carotid Intima-Media Thickness and Plaque Add to the Prediction of Stroke and Cardiovascular Disease Risk in Older Adults? The Cardiovascular Health Study

These data were presented in part at the American Heart Association Annual Scientific Sessions, Los Angeles, California, November 2012.
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Background

The aim of this study was to evaluate whether the addition of ultrasound carotid intima-media thickness (CIMT) measurements and risk categories of plaque help predict incident stroke and cardiovascular disease (CVD) in older adults.

Methods

Carotid ultrasound studies were recorded in the multicenter Cardiovascular Health Study. CVD was defined as coronary heart disease plus heart failure plus stroke. Ten-year risk prediction Cox proportional-hazards models for stroke and CVD were calculated using Cardiovascular Health Study–specific coefficients for Framingham risk score factors. Categories of CIMT and CIMT plus plaque were added to Framingham risk score prediction models, and categorical net reclassification improvement (NRI) and Harrell’s c-statistic were calculated.

Results

In 4,384 Cardiovascular Health Study participants (61% women, 14% black; mean baseline age, 72 ± 5 years) without CVD at baseline, higher CIMT category and the presence of plaque were both associated with higher incidence rates for stroke and CVD. The addition of CIMT improved the ability of Framingham risk score–type risk models to discriminate cases from noncases of incident stroke and CVD (NRI = 0.062, P = .015, and NRI = 0.027, P < .001, respectively), with no further improvement by adding plaque. For both outcomes, NRI was driven by down-classifying those without incident disease. Although the addition of plaque to CIMT did not result in a significant NRI for either outcome, it was significant among those without incident disease.

Conclusions

In older adults, the addition of CIMT modestly improves 10-year risk prediction for stroke and CVD beyond a traditional risk factor model, mainly by down-classifying risk in those without stroke or CVD; the addition of plaque to CIMT adds no statistical benefit in the overall cohort, although there is evidence of down-classification in those without events.

Section snippets

Study Population

The Cardiovascular Health Study (CHS) is a population-based prospective study of men and women aged ≥65 years at baseline. The mean age of the study population at baseline was 72.8 ± 5.6 years. The overall study design for CHS has been previously published.17 Briefly, between 1989 and 1990, CHS enrolled 5,201 participants using Medicare eligibility lists in four communities: Forsyth County, North Carolina; Sacramento County, California; Washington County, Maryland; and Pittsburgh, Pennsylvania.

Results

Of the 5,888 CHS participants, 1,406 were excluded from the analysis because of the presence of CHD, HF, or stroke at baseline. In addition, 25 were excluded because of missing carotid ultrasound data, and 73 were excluded because of missing data for the clinical covariates. Consequently, the analyses presented included 4,384 CHS participants (61% women, 14% black; mean baseline age, 72 ± 5 years). There were 482 strokes included in this analysis. Of these, 450 were classified as ischemic or

Discussion

Our study has shown that in older adults, the addition of ultrasound measurements of CIMT modestly improves 10-year risk prediction for stroke and CVD beyond the predictive ability of a traditional FRS-type risk model. This improvement is mainly the result of net improvement in down-classifying risk in participants who did not experience incident stroke or CVD. In our elderly cohort, the addition of plaque category to CIMT provided no incremental benefit in risk prediction or reclassification

Acknowledgment

The authors thank Danielle Rivas for her expert assistance in the preparation of this report.

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    This research was supported by contracts HHSN268201200036C, N01HC80007, N01 HC55222, N01HC85079, N01HC85080, N01HC85081, N01HC85082, N01HC85083, and N01HC85086 and grant HL080295 from the National Heart, Lung, and Blood Institute, with additional contribution from the National Institute of Neurological Disorders and Stroke. Additional support was provided by grant AG023629 from the National Institute on Aging. A full list of principal Cardiovascular Health Study investigators and institutions can be found at http://www.chs-nhlbi.org.

    The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

    Bijoy K. Khandheria, MD, served as guest editor for this report.

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